Do not open the window.

Let the window not be opened

Let the window not opened

Let the window not be open

Let the window not be opening

Let the window not be opens

Let the window not be opened OR you are ordered not to open the window. (Both are correct)

Active Voice: Let + indirect object + first form of a verb + direct object.

Passive Voice: Let + direct object + be + third form of a verb + by + indirect object.